lecture07 - The History of Earth and Life Lecture 07 1...

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The History of Earth and Life Lecture 07 1 Lecture 7 Overview of Previous Lectures Rocks (Main Source of Data in Historical Geology) Three Rock Types (Igneous, Metamorphic, Sedimentary) Rock Cycle and Transformation of Rock Types Formations (Lithostratigraphic Units) (Descriptive Units of Rocks - Not Time Units) Sedimentary Facies (Characteristics of Sedimentary Rocks with Environmental Implications) How to Infer History from Rocks Principles of Science Methodological Uniformitarianism (laws constant) Substantive Uniformitarianism (rates constant) Geological Processes Vary in Rates Rates Vary (linear, non-linear, episodic, cyclic) Steno's Three Principles + Cross-cutting relationship Rock Record is Incomplete (Gaps are recorded as unconformities) Based on above rock units can be ordered in time sequences Formations, Facies and Steno's Principles are not enough! Based on Steno's Principles, Cross-cutting relationships and unconformities, we can order events in temporal sequences, but. .. We do not know: How old are units? Where are time boundaries (formation or facies boundaries are not time boundaries)? How to correlate sequences across distant regions? How to correlate sequences across continents? To correlate rocks across regions and to know when they formed we need time markers and time units: Relative Time: Fossils and Biostratigraphy (Today) Absolute Time: Dating Methods (Next Lecture) Fossils, Biostratigraphy, and Relative Time Scale Organisms Change Through Time (Fact) Theory of Evolution (Theory) Biostratigraphy and Index fossils Other Relative Time Scales Time and Rock Units in Geology Geological Time Scale Fossils (=Organisms) Change through Time Fossils — The remains of ancient life The kinds of things preserved as fossils have changed with time (determined from superposition) Particular forms occur only for relatively small parts of the whole geologic column. Once a fossil form disappears from the record it does not return.
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The History of Earth and Life Lecture 07 2 Change in life through time is observed at all scales and is progressive. More presently living kinds of things are found in younger rocks than in older sediments.
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lecture07 - The History of Earth and Life Lecture 07 1...

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